1. Field of the Invention
The present invention relates to a process for producing an industrially useful decomposed rubber in the form of a liquid to a half solid state by treating vulcanized rubber with peroxide.
2. Description of the Prior Art
As a result of recent remarkable development of motorization, the amount of used tires has increased rapidly and its treatment has become a big problem. Heretofore, used tires have been used for filling-up, the structural shape itself has been used or they have been simply burned. However, these treatments are not desired from viewpoint of prevention of environmental pollution and effective use of material sources.
For the purpose of fulfilling the above-mentioned demands, reclamation of used tires has been carried out for a long time. Studies on reclaiming used vulcanized rubber has recently become active, and various new processes and agents for reclaiming have been proposed in succession.
A thermal decomposition process which is recently noted is one of treatments for used tires. In this process, used tires are thermally decomposed at a high temperature between 400.degree. C. and 900.degree. C. by a dry distillation method which is carried out under anaerobic conditions on a partial combustion method to yield gas, oil and solid residues. The resulting gas and oil are used for fuel and the resulting solid residue is used for carbon material.
There has been recently proposed a process in which vulcanized rubber is mixed with oils and decomposed at lower temperature than that of the above-mentioned process, namely, at 210.degree.-400.degree. C. in an autoclave or screw extruder to produce a molten product of vulcanized rubber. However, these processes require a higher temperature than 200.degree. C. to decompose vulcanized rubber. Therefore, it is desirable that a reclaiming process which is carried out at lower temperature, with less consumption of energy at a reduced cost is developed.
As a result of researching a process for chemically decomposing vulcanized rubber from the above-mentioned standpoint, the present inventors found a process in which vulcanized rubber can be effectively decomposed by use of diacyl peroxides at relatively low temperatures of 100.degree. C. or below, and applied said process (U.S. patent application Ser. No. 185,672). As a result of further research on a more efficient system of decomposing vulcanized rubber, the present inventors found that a peroxide system comprising an organic hydroperoxide and a particular compound is efficient for decomposing vulcanized rubber.
Although a few papers have been reported on reactions of peroxides with unvulcanized rubber and decomposition of unvulcanized rubber with peroxides, there have not been any reports on decomposition of vulcanized rubber with peroxides. It is surprising that vulcanized rubber can be easily decomposed with particular peroxides under mild reaction conditions.